Cross-linking agent and method for making same



Unid Safes Patent 2,990,316 r cRoss-LINKING AGENT AND METHOD non Wilbur' 'LBressler and calvin F. ward`,"Laknckson,

8 Claims., 10.252718@ 4 This invention relates to a crosslinking-*agent for makingjrigidpolyether typepolyurethane cellular plastic materials j Various cross-linkingpagentscan'be employed to Vcrosslink pelyurethane resinsnin rigid "polyether' Vtype polyurethane' cellular plastic material production. v Hownever, these cross-linking agentsedo not produce cellular plastic' materials whichliave excellent dimensional stability .ll jBy excellent dimensional stability, and the expression will be used hereinafter thus,"is meant that the Yc :lellular plastic materials will not distort more than l `10 volume percent, upon being subjected to the Ausual heat and/ or moisture resistance tests. When a cellular plastic material laokngdimensional stability. shrinks, itsnensity increasesjand it Ypullsavway from itsV enclosing surfaces. The shape of articles made from the cellular plastic material willv also be objectionably altered.

Two cross-linking agents which are known in rigid cellular plastic material production arel,2,3`tris(2hy droxypropyl) glycerol [,[Equaiiion 1],` ,andl octakis(2-hy droxypropyl) sucrose [Equation 2]. 1

` xide ootaiiis(Z-hydroxy-` ,-Hereinafter, 1,2,3-Itris(2hydrovypropyl )glycerol will be abbreviated "to THPG and octakis(2 hydroxypropyl) sucrose will be abbreviated to OHPSX 1 j The expression frigid foam will hereinafter be" used to mean 1a rigid lpolyether type Vpolyurethane cellular plasticmaterialffpj. .1 'i l j When THPG is `used `as a` cross-linking' agent for rigid foams, the rigid foamsexhibit ja lack of dimensional stability. For example, Yifrgid foam is prepared using THPG nals the cross linki1 tg` agent and trichlorofluoro-v methane: as thei blowing agent, the rigidfoam. Swellgreatery than p volume percent', upon being subjected to heatand/.Ofr moisture. ;I f,;inv theaboverisidfoam preparation,n water ,as the .blowing agent, the. rigid foam will shrink'greaterthan lOvolume percent,

upon being subjected to heat and/or moisture. e

WheiiOHPSisusedas across-linking agent for rigid foamsffoam preparation becomesvery diicult andthe rigid "oaniPrQdud is lijlIIllyLof` greatly varyin'g'cell size, and laeking'in dimensional stability.' These foam', faul-ts can be attributed in general' to 'the viscosity of their resist-animo siteffiug uvqnheafiss and/Qt. wetting-another O biect is. to mand fa Presets-tarnish:

Patented June 2`7, 1961 ICC ing a cross-linking agent which can be used to prepare rigid foams having excellent dimension-a1 stability. And still anotherobject is to provide' a Vcontinuous process for making a cross-linking lagent which can be used to prepare rigid foams having excellent dimensional stability. Further objects will appear from the detailed description ofV the invention which follows. 1:

It has been discovered that a mixture of THPG and OHPS is' unusually good asa cross-linking agent'v for preparing rigid foamshaving excellent dimensional stability. e v

While there is some'advantage in mixing THPG and OHPS in any ratio, the preferred rratio is about 2 to 3 moles of theV former per mole of the latter, this being the range in which (1) the rigid foam produced therefrom Vhas maximum dimensional stability and (2) the cross-linking agent is easily made and s suiciently liquid to be easily handled and mixed with the res-in to be cross-linked. e

The cross-linking agent may be prepared by simply the two components in the desired proportions; Since OHPS is so viscous as to be practically solid at ordinary temperatures and also is sensitive to deteriora'- tion by elevated temperatures, considerable care and time are required for the mixing operation if complete blending without damage is to be achieved. The two components may be stirred together, preferably with warming yto about 50-100" C., until the mixture is homogeneous. Alternatively, the two may be separately warmed and one added to the other gradually, with effective agitation. f

A preferred process for making Ithe cross-linking agent and one that largely obviates the diiiiculties inherent in making the two components separately and then mixing them, comprises dissolving sucrose' in glycerol in the desired proportions and condensing the stoichiometric amount of propylene oxide with the resulting mixture;- that is, one mole of oxide for each hydroxyl equivalent in the mixture. For this condensation a catalyst is necessary. While any tertiary amine free of labile hydrogens may be used, the preferred catalyst is triethylamine or tripropylamine. It is known that these particular amines have the peculiar property of catalyzing the condensa A tion of one, and only one, mole of prop-ylene oxide with' l substantially everyhydroxyl group on the glycol-and` sucrose is replaced with a Z-hydroxypropyl group; hence,- the product is free of polyoxypropylene derivatives. VThe use of these catalysts' for type of reaction ismore fully disclosed and claimed in the copending applications of Arthur W. Anderson, Serial No. 630,067, filed December 24, 1956, and Serial No. 658,020, tiled May 9,V 1957, now issued as U.S. Patent Nos. 2,927,9'18, and 2,902,478-

respectively. These copending applications also describe.

a preferred method for makingQHPS andTHPG. By

the term labile hydrogen we mean hydrogen sufficiently active to react with propylene oxide under the reaction conditions v'used in -tleprocess oflthe invenftion.` safe, easily controlled reaction, whichfisdlliadaptable' tocotiniiosfperation, tproduces -icolor'dcfsl n 3, Y Stokes at 210 F. The crossf agent produced by this homogeneous reaction will hereinafter be called polyol and the foams having excellent dimensional stability produced therewith are fully described and claimed in the copending application by W. L. Bressler and B. D'. Davis, filed January 29', 1959; Serial Number 789,783.

According to the preferred homogeneous reaction method for preparing the polyol, a solution is prepared by dissolving 1 mole of sucrose in from 2 moles to 3 moles of glycerol with the preferred amount of glycerol being in the range of from. 2.5 moles to 2.8` moles. When less thanZ molesof glycerol is-` used'y per 1 mole of sucrose, thesucrose does not completely dissolve and: upon cooling the finished polyol,z this-sucrose whichewasv not` originally dissolved precipitates andcauses the linished polyol .tobe cloudy. When the amount of glycerol is increased `beyond 3 molesto l; mole of sucrose,there not enough sucrose present in the finished polyol to produce rigid foams having excellent dimensional stability. To this sucrose' solution, from 0.5V percent to 2 percent, based on the totalweight ofsucrose and, glycerol,Y tertiary amine, preferably triethylamine or tripropylamine, is added as a reaction catalyst and, optionally but preferably,` from 0.5 to about 2. percent-water also based on the total weight of sucrose and glycerol. The preferred amount ofv tertiary amine is from 0.8v to l percent. When less than 0.5 percent is used, thev reaction proceeds very slowly, and when more than 2 percent is used, the reaction is so rapid that temperature control is diiiicultand the resulting product is usually dark colored. The tertiary amine canbe selected from those aliphatic, heterocyclic, or aryl amines, or; combinations thereof, which are soluble in the reaction media and which have no other functional groups containing. labile hydrogen. Representative cornpounds include triethylamine, N-methylmorpholine,` dirnethylaniline,- methyldiethylamine,` and dimethylethylamine. It has been found desirable, though not essential', thatl the sucrose-glyceroll mixture contain a small proportion of'water. It has been foundthat when thereaction is run without water, the reactants must be; heated to about 120 C. to start the reaction. Once the reaction has begun, the temperature rises rapidly and; the polyol may develop a. dark color. When Water isf present in the reaction mixture,.the reactionwill proceed with excellent resultsat a temperatureofi about 100 C. and the resulting polyol is not colored; A suitable amount; is about.0.52 percent by'weighttabout 5 to 20.mole percent).

Tor this sucrose solution containing catalyst and water, a:stoichi'ometricV amount'ofipropylene oxide isv added over aperiod of from 2 to 40. hours While the reaction mass is-maintained at a temperature from. about 90 toA about 120, and preferably atv a temperature ofn about 100 C.. while under a. pressure at leastl equal toautogenous pressure. Theiinished' polyol usually has a viscosityv of about 160 to 200 stokes at 210 F.

A preferred method of preparing.: the polyol continuously uses a one-pass coil reactorV jacketed: for steam and: water, a pump for supplyingy propylene oxide to the reactor, and a pump forV supplyingzthe glycerol-sucrose mixture to the reactor. The reactor is maintained at a-temperature of from 90 to1l0 C. and a pressure of atleastk 100 p.s.i.g. The desired feed rate is such that the retention time in the reactorv is atleast about 2.y

EXAMPLE 1.-POLYOL PREPARATION Into a reaction vessel equipped with a meansv for stirring,` temperature control, and maintaining amethane atn'losphere 'were placedl 17.1 pounds of rened* beet;

sugar, 11.5 'pounds of glycerol andl 1:05; grams of'tni'ethyl amine` catalyst'. The mixture was preheated to'130`` C.

after which 45 pounds of. propyle'ne` oxide was addedover a 12-hour period. During this period, the pressure maintained by the propylene oxide was from about 30 to about 40 p.s.i.g. and .the temperature was maintained at about 125 to 135 C. Upon completion of the propyl ene oxide addition, the reaction mixture was digested for 2 hours at approximately 130 C. At the end of the 2- hour digestion period, ythe pressure in the vessel was reduced to 5 absolute, and maintained thereat for 15 minutes while maintaining the temperature at about 130 C. The product had the following properties:

Viscosity=182 stokes at 210 F. APHA. color= 250Y EXAMPLE 2.-POLYOL PREPARATION The-polyol was prepared. asin Example 1- with the exception that renedcane, sugar wasused instead of beet sugar.

Viscosity=181 Stokes at 210 F.

APHA color= 25l0 y l EXAMPLE' S-POLYOL PREPARATION' Y p Into a reaction vessel equipped with a meansY for stirring,.temperature control', and maintaining a methane atmosphere'were placed 17.1' pounds ofY beet sugar, 11.5 pounds of glycerine,- andv -105 grams of triethylamine catalyst. The mixture was preheated to C., after which 45 poundsof propylene oxide was added over a 6- hour period. During period, the pressure was maintained. by the. propylene oxide at. about 40 to 50 p.s.i.g. andthe temperature was maintained at about 90 C.. Upon completion of the propylene oxide. addition, the reaction mixturey was. digested for 2 hours at approximately C. At the end of the Zrhour diges.- tion period, the pressurefinthe. vessel was reduced to 5 mm., absolute, and maintainedy thereatA for 15 minutes while maintaining the temperatureatabout 100 C. The product` had the following, properties:

Stokes at 21.0.' F. APHA co1or= 200 EXAMPLE 4.POLYOL PREPARATION Into a reaction vessel equipped with. aV means for stirring, temperature control, and maintainingamethane atmosphere were placed 17.1 pounds of beet sugar, 11.5 pounds-of glycerol, 2.10vr grams oftriethylamine catalyst, andZIOgrams offwater. The mixture was'preheated to 100 C., after whichz45pounds1of propylene'oxidewas added over a l2-hour time period.v During this period, the pressurev maintained byv thepropylene oxide at from about 40 to about 50 p.s.i.g. and the temperature was maintained at about 100 C. Upon completion:y of the propylene oxideY addition, the reaction mixture-Was digestedl for 2 hours' at approximately 100v C. Ati the end' of" the digestion period; thepressure in the vessel was reduced" to 5- mm., absolute, and maintained thereat for 1'5 minutes-while maintaining the'temperature ati about 100 C'. Theproduct hadithe following properties: Viscosity=179.5 stokes at.2l10 F.

APHA O010r=90 EXAMPLE 5`.-POLYOL PREPARATION The polyolA was prepared as in Example 4 with the exception that grams of niethylamine catalyst was' used insteadv of 2x10 grams. v

Visccsity= APHA. co1or=70 EXAMPLE 6.-CONTINUOUS PREPARATION 0F POLYOLV Ar feed solutionv was prepared=- by placing: into-a action'l vessel, equipped; withv amcansfor stirring zand? temperature1 control, 42:75:? poundsr` ofiy beet' sugar,'..2'875 held `at aboutlOO p.s.i.g. At the same time, a second micro metering pump pumped propylene oxide at the rate of 590 ml. per hour to the reactor; These two feed rates lWere'such fthat the retention time fof thedr'eotnts in the reactor was about 4 hours. After being devolatilized, the nished polyol had the following properties:

APH color=90 EXAMPLE 7.-POLYOL PREPARATION Into a reaction vessel equipped with a means for stirring, temperature control, and maintaining a methane atmosphere were placed 17.1 pounds of refined cane sugar, 11.5 pounds of glycerol, 105 grams of triethylamine catalyst, and 208 grams of water. 'I'he mixture was preheated to 100 C., after which 34 pounds of ethylene oxide was added over a 4-hour period. During this period, the pressure was maintained by the ethylene oxide at about 40 to about 50 p.s.i.g. and the temperature was maintained at about 100 to 110 C. IUpon completion of the ethylene oxide addition, the reaction mixture was digested for 2 hours at approximately 110 C. At the end of the digestion period, the pressure in the vessel was reduced to mm., absolute, and maintained thereat for 15 minutes while maintaining the temperature at about 120 C. The product had the following properties:

Viscosity=53 centistokes 210 F. APHA color: 100

EXAMPLE 8.-POLYOL PREPARATION Into a reaction vessel equipped with a means for stirring, temperature control, and maintaining a methane atmosphere were placed 17 .1 pounds of refined cane sugar, 11.5 pounds of glycerol, 105 grams of triethylamine catalyst, and 208 grams of water. The mixture was preheated to 110 C., after which 55.8 pounds of butylene oxide was added over a 4-hour period. During this period, the pressure was maintained by the butylene oxide at about 20 to 30 p.s.i.g. and the temperature was maintained at about 100 to 110 C. Upon completion of the butylene oxide addition, the reaction mixture was digested for 2 hours at approximately 110 C. At the end of the digestion period, the pressure in the vessel was reduced to 5 mm., absolute, and maintained thereat for l5 minutes While maintaining the temperature at about 120 C. The product had the following properties:

Viscosity=53 centistokes at 210 F. APHA color: 80

EXAMPLE 9.-1FOAM PREPARATION lUSING THPG AS THE CROSS-LINKING AGENT Component A Component A consisted of 165 grams of 'II-IPG semiprepolymer and 32.5 grams of trichlorofluoromethane. I'he THPG semiprepolymer was prepared in the followmg manner:

Into a reaction vessel equipped with a means for heating, temperature control, and maintaining a nitrogen atmosphere were placed 9750 grams of toluene diisocyanate. The toluene diisocyanate was then preheated to 60 C., after which 2,430 grams of 1,2,3tris(hydroxy propyl) glycerol were added over a 45-minute period. During this period, the temperature of the reaction vessel was maintained between 55 and 60 C. The THPG semiqprepolyrner thus produced hada viscosity `at 249 C. of stokesandan NCO content of 27.5 percent.

VComponent B 4Compone'nt'B consisted of 84.67'grams of THPG, 0.6

gram 'of .niethylenediamine, and 0.3 gram of 'Silicone `XL'-520 (Organos-ilicone polymer made by Union Carbide). z

The components, A and B, were thoroughly mixed for 20 -seconds and immediately pouredinto va rectangular mold.' The mass expanded and had the following properties: u

.. l 5i-; `84 percent closed cells Density=2.2

'I'he foam swelled l1 percent while being subjected to 16 hours in the humidity-ageing chamber. This chamber maintains a humidity of 98 percent at a temperature of .158 Ri-2.

EXAMPLE 10.--FOAM PREPARATION USING PRO- PYLENE OXIDE POLYOL AS THE CROSS-LINK- ING AGENT Component A Component A consisted of 160 grams of THPG semiprepolymer, prepared as in Example 9 and 21.5 grams of trchloroiiuoromethane.

Component B 'Ihe foam swelled 3 percent while being subjected to 192 hours in the humidity-ageing chamber.

EXAMPLE 1l.-FOAM PREPARATION 'USING OHPS AS THE CROSS-LINKING AGENT An attempt `at foam preparation as in Example 10 was made by preparing a component A consisting of blowing agent and the THPG semiprepolymer. The quantity of OHPS required for component B was heated to about 67 C. in order to get it from a solid state to a heavy, viscous state. At this temperature, the tertiary amine and Silicone XL-520 were stirred in. When hot component B was added to cold component A, the reaction was so rapid that stirring could not be accomplished and further, a major portion of the blowing agent vaporized and was lost. The pro-duct was a somewhat foamed lumpy mass and no attempt at property evaluation was made.

The polyol products of the invention are especially useful for cross-linking Afoamed urethane resins as hereinbefore set forth. Also, they are useful as softeners and plasticizers for paper, cellophane and other cellulosic materials and as intermediates in the production of alkyd resins, surfactants, drying oil esters and the like.

We claim:

,'1. A composition comprising the polyol product formed by the reaction of l) a mixture of one mole of sucrose, about 2-3 moles of glycerol and about 0-1 mole of water with (2) one mole of propylene oxide per hydroxyl equivalent in said sucrose, glycerol and water, said reaction being conducted in the presence of a catalytic amount of a tertiary amine free of labile hydrogen, at a temperature of about to 140 C. and under a pressure at least equal to the autogenous pressure.

2. A composition as defined in claim 1, the amine used as a catalyst in its production being a trialkylamine.

3. A composition as defined in claim l, the amine used as a catalyst in' its production being triethylam-ine.

4'. A'cbrpos'itionas defned'n cl'airn 1, the' 'mixture of sucrose and` g1`ycero1` used' in its production containing about 0.2 to 0.4 moleowatexr;

5. A process comprising reacting by contacting. in a phase at` a temperature ofaBout-,8O-140ff C. and Qn'fth lpresence of a catalytic.amountl oie. tertiary amine free of labile hydrogen (1) a mixture-fof one moleyof sucrose,v about` 2- tof- 3 moles of glycerolA andr O- toabout 0:4mo1e of water and. (-2) at least about one mo1e= of `propylenefoxide p'er hydroxyl equivalent in said sucrose, glycerol and water.

6. A process asdefnedlinrclaimi 5 wherein the amine is a trialkylamine.

r B10-@111.l et a1. Aug. 26.4 195s w 2,86657'74` Pcef Y Dec'. 30 1958 2,902,478- Anderson Y Sept. l', 1959 FOREIGN PATENTS Great Britain Feb. 27, 1957 

1. A COMPOSITION COMPRISING THE POLYOL PRODUCT FORMED BY THE REACTION OF (1) A MIXTURE OF ONE MOLE OF SUCROSE, ABOUT 2-3 MOLES OF GLYCEROL AND ABOUT 0-1 MOLE OF WATER WITH (2) ONE MOLE OF PROPYLENE OXIDE PER HYDROXYL EQUIVALENT IS SAID SUROSE, GLYCEROL AND WATER, SAID REACTION BEING CONDUCTED IN THE PRESENCE OF A CATALYTIC AMOUNT OF TERTIARY AMINE FREE OF LABILE HYDROGEN, AT A TEMPERATURE OF ABOUT 80 TO 140* C. AMD UNDER A PRESSURE AT LEAST EQUAL TO THE AUTOGENOUS PRESSURE. 